Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. A method for characterizing an N-qubit process, N being an integer greater than 2, the method comprising: performing a plurality of characterization measurements of the N-qubit process to form a plurality of process maps, and fitting the plurality of process maps with a composition of K-qubit processes, K being an integer greater than 1 and less than N.
This invention relates to quantum computing, specifically to methods for characterizing multi-qubit processes. The problem addressed is the complexity of accurately modeling and characterizing quantum processes involving multiple qubits, which is essential for error correction, optimization, and improving quantum gate fidelity. Traditional methods often struggle with scalability and computational efficiency when dealing with N-qubit systems where N is greater than 2. The method involves performing multiple characterization measurements of an N-qubit process to generate a plurality of process maps. These process maps are then fitted using a composition of K-qubit processes, where K is an integer greater than 1 but less than N. This decomposition approach simplifies the characterization by breaking down the N-qubit process into smaller, more manageable K-qubit sub-processes. The fitting step ensures that the combined K-qubit processes accurately represent the original N-qubit process, enabling precise modeling and analysis. By leveraging this decomposition technique, the method reduces the computational complexity associated with characterizing large-scale quantum processes. This is particularly useful in quantum error correction, gate calibration, and benchmarking, where accurate process characterization is critical. The approach is scalable and adaptable to various quantum hardware platforms, making it a valuable tool for advancing quantum computing research and development.
2. The method of claim 1 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with a method that excludes state-preparation and measurement errors.
This invention relates to quantum computing, specifically improving the accuracy of quantum characterization measurements. Quantum systems are highly sensitive to errors during state preparation and measurement, which can distort characterization results and reduce the reliability of quantum computations. The invention addresses this by performing characterization measurements using techniques that exclude or mitigate state-preparation and measurement errors. This ensures that the measurements accurately reflect the true properties of the quantum system, such as gate fidelities or qubit coherence times, without being skewed by external noise or imperfect operations. The method involves applying error-resistant measurement protocols, such as randomized benchmarking or gate set tomography, while actively suppressing or correcting errors during the process. By isolating the system from preparation and measurement inaccuracies, the technique provides more precise and trustworthy quantum system characterization, which is critical for advancing quantum hardware and algorithms. The approach is particularly useful in noisy intermediate-scale quantum (NISQ) devices, where error sources are prevalent but full error correction is not yet feasible.
3. The method of claim 2 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with gate set tomography.
This invention relates to quantum computing, specifically to methods for characterizing quantum devices. The problem addressed is the need for accurate and efficient characterization of quantum gates and circuits to ensure reliable quantum computation. Traditional characterization methods may be time-consuming or lack precision, leading to errors in quantum operations. The invention describes a method for characterizing quantum devices by performing a plurality of characterization measurements. These measurements are conducted using gate set tomography, a technique that reconstructs the quantum operations of a gate set by analyzing the outcomes of multiple experiments. Gate set tomography provides a comprehensive characterization of quantum gates, including their error rates and fidelity, by comparing experimental results with theoretical predictions. The method involves applying a set of quantum gates to qubits, measuring the resulting quantum states, and analyzing the measurement data to determine the properties of the gates. This approach allows for precise calibration and error mitigation in quantum circuits, improving the overall performance of quantum devices. The characterization measurements are performed in a controlled manner to ensure accuracy and reproducibility. The method may include iterative processes to refine the characterization results, such as adjusting experimental parameters or repeating measurements to reduce noise and statistical errors. By using gate set tomography, the invention provides a robust framework for assessing the performance of quantum gates, enabling the development of more reliable quantum computing systems.
4. The method of claim 1 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a maximally mixed state; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This invention relates to quantum computing, specifically to techniques for characterizing quantum circuits by isolating the behavior of specific qubits while mitigating the effects of other qubits in the system. The problem addressed is the difficulty in accurately measuring the performance of a subset of qubits in a quantum processor, as interactions with other qubits can introduce noise and errors that obscure the true behavior of the qubits of interest. The method involves selecting a subset of K qubits to be characterized while treating the remaining N-K qubits as "spectator" qubits. The K qubits are initialized in a defined quantum state, while the spectator qubits are prepared in a maximally mixed state, which effectively randomizes their initial conditions to minimize their influence on the measurement. A quantum circuit comprising one or more gates is then applied to both the K qubits and the spectator qubits. After the circuit is executed, only the state of the K qubits is measured, allowing for the isolation of their behavior from the effects of the spectator qubits. This approach enables more accurate characterization of the quantum gates and operations performed on the qubits of interest, improving the reliability of quantum circuit testing and calibration. The technique is particularly useful in large-scale quantum systems where qubit interactions and environmental noise can complicate measurements.
5. The method of claim 1 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a state randomly selected from a uniform distribution of the set of spectator qubit logical states; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This invention relates to quantum computing, specifically to methods for characterizing quantum circuits by measuring qubit states in the presence of spectator qubits. The problem addressed is the need to accurately assess the performance of quantum circuits while accounting for interactions with other qubits in the system. The method involves selecting a subset of K qubits of interest from a total of N qubits, where the remaining N-K qubits act as spectator qubits. The spectator qubits are initialized in random states drawn uniformly from a predefined set of logical states. A quantum circuit, comprising one or more gates, is then applied to both the qubits of interest and the spectator qubits. After circuit execution, only the state of the K qubits of interest is measured, while the spectator qubits are not directly measured. This approach allows for the characterization of quantum circuits under realistic conditions where qubits interact with their environment, providing more accurate performance metrics. The random initialization of spectator qubits ensures that the characterization accounts for potential variations in their states, improving the robustness of the measurement results. This technique is particularly useful for benchmarking quantum hardware and validating quantum algorithms.
6. The method of claim 1 , wherein K=2.
7. The method of claim 6 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with a method that excludes state-preparation and measurement errors.
This invention relates to quantum computing, specifically improving the accuracy of quantum characterization measurements. Quantum systems are highly sensitive to errors during state preparation and measurement, which can distort characterization results and reduce the reliability of quantum computations. The invention addresses this by performing characterization measurements using techniques that exclude or mitigate state-preparation and measurement errors. This involves applying error-correction methods or alternative measurement protocols that isolate the quantum system from external noise and inaccuracies during the characterization process. By eliminating these error sources, the method ensures that the collected data accurately reflects the true properties of the quantum system, enabling more precise calibration and control. The approach can be applied to various quantum hardware platforms, including superconducting qubits, trapped ions, or photonic systems, where measurement fidelity is critical. The invention enhances the reliability of quantum experiments and computations by providing a more accurate characterization of quantum states and operations.
8. The method of claim 7 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with gate set tomography.
This invention relates to quantum computing, specifically to methods for characterizing and improving the performance of quantum gates. The problem addressed is the need for accurate and efficient characterization of quantum gates to ensure reliable quantum computation. Quantum gates are fundamental building blocks in quantum circuits, but their performance can degrade due to errors, noise, and imperfections in hardware. Accurate characterization is essential for error correction and optimization. The method involves performing a plurality of characterization measurements on a quantum system to assess the performance of quantum gates. These measurements are conducted using gate set tomography, a technique that reconstructs the quantum operations applied to a system by comparing input states, output states, and measurement outcomes. Gate set tomography provides a comprehensive characterization of the quantum gates, including their fidelity, error rates, and other performance metrics. The characterization data obtained from gate set tomography is then used to adjust the quantum gates to improve their performance. This adjustment may involve modifying gate parameters, applying error correction techniques, or optimizing pulse sequences to reduce errors. The goal is to enhance the accuracy and reliability of quantum computations by refining the quantum gates based on the characterization results. By integrating gate set tomography into the characterization process, the method ensures a high level of precision in assessing and improving quantum gate performance, which is critical for advancing quantum computing technology.
9. The method of claim 6 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a maximally mixed state; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This invention relates to quantum computing, specifically to techniques for characterizing quantum circuits by isolating the behavior of a subset of qubits while accounting for the influence of other qubits in the system. The problem addressed is the need to accurately measure the properties of specific qubits in a quantum processor without being unduly affected by the states of neighboring or interacting qubits, which can introduce noise or errors in the characterization process. The method involves selecting a subset of K qubits of interest from a total of N qubits in a quantum system. These K qubits are prepared in a specific initial state, while the remaining N-K qubits, referred to as spectator qubits, are prepared in a maximally mixed state. This ensures that the spectator qubits do not introduce bias or unwanted correlations into the measurement of the K qubits. A quantum circuit, consisting of one or more quantum gates, is then applied to both the K qubits and the N-K spectator qubits. After the circuit is executed, only the state of the K qubits of interest is measured, while the state of the spectator qubits is ignored. This approach allows for precise characterization of the behavior of the K qubits under the influence of the applied gates, while mitigating the effects of the spectator qubits. The technique is useful for calibrating quantum processors, validating gate operations, and improving the accuracy of quantum computations.
10. The method of claim 6 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a state randomly selected from a uniform distribution of the set of spectator qubit logical states; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This invention relates to quantum computing, specifically to methods for characterizing quantum circuits by isolating the behavior of selected qubits while accounting for the influence of other qubits in the system. The problem addressed is the difficulty in accurately measuring the performance of specific qubits in a multi-qubit system, where interactions with other qubits can introduce noise and errors that obscure the true behavior of the qubits of interest. The method involves selecting K qubits of interest from a total of N qubits in a quantum system. The remaining N-K qubits, referred to as spectator qubits, are prepared in random states drawn from a uniform distribution of possible logical states. A quantum circuit comprising one or more gates is then applied to all N qubits, including both the qubits of interest and the spectator qubits. After the circuit is applied, only the states of the K qubits of interest are measured. By randomizing the states of the spectator qubits, the method averages out their influence on the qubits of interest, allowing for a more accurate characterization of the behavior of the selected qubits in the presence of the full system. This approach is useful for identifying and mitigating errors in quantum circuits, optimizing gate operations, and improving the overall reliability of quantum computations.
11. A system, comprising: an N-qubit device; and a processing circuit, connected to the N-qubit device, the processing circuit being configured to: perform a plurality of characterization measurements of an N-qubit process to form a plurality of process maps, and fit the plurality of process maps with a composition of K-qubit processes, K being an integer greater than 1 and less than N.
This invention relates to quantum computing, specifically to the characterization and modeling of multi-qubit processes in quantum systems. The problem addressed is the complexity of accurately characterizing and modeling the behavior of large-scale quantum systems, where direct measurement of all possible interactions becomes computationally infeasible. The solution involves a system that includes an N-qubit device and a processing circuit connected to it. The processing circuit performs multiple characterization measurements of an N-qubit process to generate a set of process maps. These process maps are then fitted with a composition of K-qubit processes, where K is an integer greater than 1 and less than N. This approach decomposes the complex N-qubit process into smaller, more manageable K-qubit sub-processes, simplifying the characterization and modeling process. The method leverages the fact that many quantum processes can be approximated by combinations of lower-dimensional processes, reducing the computational and experimental overhead required for full characterization. This technique is particularly useful for error mitigation, process tomography, and improving the accuracy of quantum algorithms in noisy intermediate-scale quantum (NISQ) devices.
12. The system of claim 11 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with a method that excludes state-preparation and measurement errors.
This invention relates to a system for performing quantum characterization measurements with reduced errors. The system addresses the challenge of accurately characterizing quantum systems, which is often hindered by state-preparation and measurement errors that introduce inaccuracies into the results. The system includes a quantum processor configured to execute quantum circuits and a controller that directs the processor to perform a series of characterization measurements. The measurements are conducted using a method that specifically avoids state-preparation and measurement errors, ensuring higher fidelity in the characterization process. The system may also include a memory for storing measurement data and a communication interface for transmitting the data to an external device for analysis. The controller is further configured to process the measurement results to extract quantum system properties, such as gate fidelities or qubit coherence times, while minimizing the impact of errors. The system may also incorporate error mitigation techniques to further refine the characterization outcomes. By excluding state-preparation and measurement errors from the characterization process, the system provides more reliable and precise quantum system assessments, which are critical for advancing quantum computing and related technologies.
13. The system of claim 12 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with gate set tomography.
A system for characterizing quantum computing devices performs a plurality of characterization measurements to assess the performance of quantum gates. The system includes a quantum processor with qubits and control hardware for executing quantum circuits. The characterization measurements are performed using gate set tomography, a technique that reconstructs the actual quantum gates applied to the qubits by comparing the observed outputs of quantum circuits to expected outputs. This allows for the determination of gate errors, fidelity, and other performance metrics. The system may also include calibration hardware to adjust the quantum processor based on the characterization results, ensuring accurate and reliable quantum operations. The measurements are conducted under controlled conditions to minimize external noise and interference, providing precise data for analysis. The system may further include data processing components to analyze the measurement results and generate reports or recommendations for improving quantum gate performance. By using gate set tomography, the system provides a comprehensive and accurate assessment of quantum gate behavior, enabling optimization of quantum computing operations.
14. The system of claim 11 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a maximally mixed state; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This invention relates to quantum computing, specifically to methods for characterizing quantum circuits by leveraging spectator qubits to reduce measurement overhead. The problem addressed is the high resource cost of traditional quantum circuit characterization, which often requires extensive measurements to assess performance. The solution involves using a subset of qubits (K qubits of interest) while treating the remaining qubits (N-K spectator qubits) as a maximally mixed state. This approach reduces the number of measurements needed by focusing only on the qubits of interest while the spectator qubits act as a noise-averaging background. The process begins by initializing the K qubits in a specific state and the spectator qubits in a maximally mixed state. A quantum circuit with one or more gates is then applied to all qubits. After circuit execution, only the K qubits of interest are measured, while the spectator qubits are ignored. This method improves efficiency by minimizing the number of qubits that need to be measured, thereby reducing the overall measurement overhead while still providing accurate characterization of the circuit's performance. The technique is particularly useful in large-scale quantum systems where full-state tomography is impractical.
15. The system of claim 11 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a state randomly selected from a uniform distribution of the set of spectator qubit logical states; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This system is designed to characterize the behavior of a quantum process involving N qubits (where N is greater than 2). It operates by performing multiple characterization measurements to generate various "process maps" of the N-qubit process. These maps are then analyzed by fitting them to a composite model of smaller K-qubit processes, where K is greater than 1 but less than N. Specifically, when the system performs one of these characterization measurements, it follows these steps: It first prepares a subset of K "qubits of interest" in a defined initial quantum state. At the same time, the remaining N-K "spectator qubits" are prepared in a randomly selected state from a uniform distribution of all possible spectator qubit logical states. Next, a quantum circuit, comprising one or more gates, is applied to both the K qubits of interest and the N-K spectator qubits. After the circuit's execution, the system measures the resulting quantum state of only the K qubits of interest.
16. The system of claim 11 , wherein K=2.
17. The system of claim 16 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with a method that excludes state-preparation and measurement errors.
This invention relates to quantum computing systems, specifically addressing the challenge of accurate characterization of quantum devices. Quantum systems are highly sensitive to errors during state preparation and measurement, which can distort characterization results and reduce the reliability of quantum operations. The invention describes a system that performs a plurality of characterization measurements on a quantum device, where the measurements are conducted using a method that intentionally excludes state-preparation and measurement errors. By isolating these error sources, the system achieves more precise and reliable characterization of quantum states and operations. The characterization measurements may include techniques such as quantum process tomography, gate fidelity assessment, or qubit coherence time evaluation. The system may also incorporate error mitigation strategies, such as post-processing corrections or adaptive measurement protocols, to further enhance accuracy. The exclusion of state-preparation and measurement errors ensures that the characterization results reflect the true performance of the quantum device, enabling more effective calibration, optimization, and control of quantum operations. This approach is particularly valuable in noisy intermediate-scale quantum (NISQ) devices, where error sources are significant and must be carefully managed.
18. The system of claim 17 , wherein the performing of the plurality of characterization measurements comprises performing the characterization measurements with gate set tomography.
A system for characterizing quantum computing hardware performs a plurality of characterization measurements to assess the performance of quantum gates and circuits. The system includes a quantum processor with qubits and control circuitry configured to execute quantum operations. The characterization measurements are performed using gate set tomography, a technique that reconstructs the actual quantum operations implemented by the hardware from experimental data. This involves applying a set of known input states, measuring the resulting output states, and comparing them to expected outcomes to determine the fidelity and accuracy of the quantum gates. The system may also include calibration modules to adjust gate parameters based on the characterization results, ensuring optimal performance. The measurements are used to generate a model of the quantum hardware's behavior, which can be used to correct errors and improve the reliability of quantum computations. This approach helps identify deviations between the intended and actual gate operations, enabling more precise control and higher fidelity in quantum computing applications. The system is particularly useful for validating and optimizing quantum processors in research and industrial settings.
19. The system of claim 16 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a maximally mixed state; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This invention relates to quantum computing, specifically to methods for characterizing quantum circuits by isolating the behavior of specific qubits while mitigating the effects of other qubits in the system. The problem addressed is the difficulty in accurately measuring the performance of a subset of qubits in a quantum processor, as interactions with other qubits can introduce noise and errors that obscure the true behavior of the qubits of interest. The system prepares a quantum circuit for characterization by dividing the qubits into two groups: a subset of K qubits of interest and N-K spectator qubits. The K qubits are initialized in a defined first state, while the remaining N-K spectator qubits are prepared in a maximally mixed state, which effectively randomizes their initial conditions. This randomization helps to average out their influence on the measurement results, reducing the impact of their interactions with the qubits of interest. A quantum circuit comprising one or more gates is then applied to both the K qubits and the spectator qubits. After the circuit execution, only the state of the K qubits is measured, allowing for the isolation and characterization of their behavior without interference from the spectator qubits. This approach enables more accurate and reliable assessment of the performance of specific qubits in a quantum system.
20. The system of claim 16 , wherein the performing of a characterization measurement of the plurality of characterization measurements comprises: preparing K qubits of interest in a first state; preparing N-K spectator qubits in a state randomly selected from a uniform distribution of the set of spectator qubit logical states; applying a circuit comprising one or more gates to the K qubits of interest and to the N-K spectator qubits; and measuring, after the applying of the circuit, the state of the K qubits of interest.
This invention relates to quantum computing, specifically to methods for characterizing quantum circuits by isolating the behavior of selected qubits while accounting for the influence of other qubits in the system. The problem addressed is the difficulty in accurately measuring the performance of specific qubits in a multi-qubit quantum system, where interactions with neighboring qubits can introduce noise and errors that obscure the true behavior of the qubits of interest. The system prepares K qubits of interest in a predefined initial state while the remaining N-K spectator qubits are initialized to random states drawn from a uniform distribution of possible logical states. A quantum circuit comprising one or more gates is then applied to both the qubits of interest and the spectator qubits. After the circuit execution, only the final state of the K qubits of interest is measured, effectively isolating their behavior while accounting for the statistical influence of the spectator qubits. This approach allows for more accurate characterization of the qubits of interest by averaging over the random states of the spectator qubits, reducing the impact of their specific configurations on the measurement results. The method is particularly useful for benchmarking and error analysis in quantum computing systems.
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October 27, 2020
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